In conjunction with the operation of any internal combustion engines various forms of exhaust gas treating apparatus are known and used having the general purpose of protecting the atmosphere and the environment. One form of such treating apparatus includes a catalytic converter or treating unit wherein hot exhaust gases are received, and harmful components are reduced in quantity by oxidation, or eliminated through chemical reaction. Thus, as treated exhaust gas leaves the filter or the converter, the gas is relatively harmless. Further, it is free of solid particles, and can be safely discharged into the atmosphere without fear of polluting or damaging the latter to any extent.
Such catalytic converters or filters are normally so positioned with respect to the engine as to receive the exhaust gases in as hot a condition as possible. Thus, the catalyst is rapidly raised to, and remains at this elevated operating temperature. Further, the unit is normally subjected to considerable physical abuse. This is particularly true in the instance of an automotive or similar motor vehicle wherein vibration and severe movements act adversely upon the filter.
Ordinarily, when the internal combustion engine is at rest, the catalytic filter will be at substantially atmospheric temperature. However, upon being started, the engine will discharge a relatively hot exhaust gas which, within a short period of time, can climb to a temperature of 700.degree. to 1100.degree. F. In addition, prolonged exposure to such high temperatures can physically weaken the structure. It is appreciated that the combustion of such wide temperature differentials and continuous high temperatures acting upon the filter, will be detrimental to both the filter's structure and the operation thereof.
It has been found that under severe circumstances of temperature, as well as engine and vehicle vibration, the catalyst bed can sustain gradual damage by a separation of the catalytic material from the carrier or substrate. Further, such vibration can cause the filter material to become spaced from the filter casing walls thereby permitting at least part of the exhaust gases to channel past the catalyst bed. Continued use over a period of time will widen said channels. Said bypass gas will subsequently increase in volume and be discharged to the atmosphere in an untreated condition.
A further detriment experienced in such smoke filters resides in the excessive back pressure encountered. This results from excessive accumulations on the catalyst surfaces. Such a circumstance will tend to inhibit proper functioning of the filter to its maximum capacity, and will lessen the efficiency of the engine on which it is used.
Toward overcoming these above noted difficulties, the present arrangement includes in essence a catalytic converter or smoke filter particularly adapted for treating and for removing harmful particles such as carbon and the like from an exhaust gas stream. This is achieved by passing the latter through a series of braced and supported, yet separated catalytic beds such that chemical reactions within the latter dispose of the carbon thereby resulting in a relatively clean residual gas.
An object of the invention then is to provide a compact, relatively rugged filter unit capable of cooperating with an internal combustion engine to treat exhaust gases leaving the latter. A further object is to provide means for minimizing the thermal and physical shock on the catalyst material normally caused during the operation of an internal combustion engine under certain circumstances of engine load. A still further objective is to provide an exhaust gas treatment unit having a series of catalyst beds disposed therein, capable of withstanding sustained physical vibrations of shock as well as severe temperature gradients. Another object is to provide a filter structure which is capable of minimizing filter back pressure during operation thereof.